Stage I fatigue cracking in MAR-M 247 superalloy at elevated temperatures

Nickel base superalloys exhibit fatigue fracture behavior with features of brittle-like cleavage cracking under high cycle fatigue loading at temperatures up to approximately 800 °C. This specific fracture behavior was already documented in several studies, but a possible mechanism of fatigue crack propagation under this mode has not been made completely clear yet. The aim of this paper is to put more light on the phenomenon by using advanced electron microscopy techniques like electron back-scattered diffraction (EBSD) and focused ion beam (FIB) sectioning. Fractured specimens after high cycle fatigue tests were thoroughly examined with the aim to localize the fatigue crack initiation sites and accompanying features of the fatigue crack propagation. Several specimens were cross-sectioned in order to characterize active slip systems, cyclic plastic deformation localization and fatigue crack propagation. Dislocation structures were studied by transmission electron microscopy (TEM).

Keywords

Superalloy, High cycle fatigue, Elevated temperature, MAR-M 247, Fatigue crack initiation

Citation

Procedia Structural Integrity. 2016, vol. 2, issue 1, p. 3018-3025.
http://www.sciencedirect.com/science/article/pii/S2452321616303961

Document type

Peer-reviewed

Document version

Published version

Language of document

en

Document licence

Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
http://creativecommons.org/licenses/by-nc-nd/4.0/